STEM CELLS, CLONING AND REGENERATIVE MEDICINE The basics

Stem Cells

First we need to review “normal” reproduction . . . HAPLOID gametes are produced by meiosis During fertilization, the sperm cell deposits its chromosomes into the egg The egg cell is now fertilized, has DNA from 2 sources, and is DIPLOID We call this cell a zygote

What happens to the zygote? The zygote begins rapid cell division and divides into a ball of cells called the embryo. This is done by mitosis so all of the cells in the embryo are genetically identical. Within a few days, the middle of the embryo hollows out and we call the resulting embryo a blastocyst.

How big is a blastocyst?

Here’s where the process happens:

So what happens after the embryo is created? In adults, most cells are specialized for tasks: Red blood cells carry oxygen Neurons transmit electrical signals Pancreatic cells secrete insulin Cells of the embryo “commit” to a particular fate or decide which specialized cell type they will become. This process is called differentiation The genes expressed will determine what cell type they will become or differentiate into. Epigenetics is important for this process!

Cell Differentiation

Stem Cell Basics Stem cells: Cells that have yet to differentiate and have the ability to divide repeatedly There are lots of varieties of stem cells embryonic, adult, umbilical, amniotic, induced pluripotent Depending on source, potency may vary

Stem Cell Potencies Stem Cell Type Description Example totipotent Each cell can develop into a new individual 1-3 days old embryo pluripotent Cells can form over 200 cell types 5-14 days embryo multipotent Cells differentiated but can form multiple cell types Cord blood, adult stem cells

Research Potential of Stem Cells

Embryonic Stem Cells (ESCs) ESC are derived from the inner cell mass of the blastocyst stage (5 days old) These cells are pluripotent

Potential Uses of ESCs Repair a damaged tissue or cells that can't heal itself This might be accomplished by transplanting stem cells into the damaged area and directing them to grow new, healthy tissue. It may also be possible to coax stem cells already in the body to work overtime and produce new tissue. Tissue/organ growth and transplants?

Cultured embryonic stem cells (developing an ESC line) ESCs can be cultured in different laboratory environments to develop into a specific cell type: Liver cells Cultured embryonic stem cells (developing an ESC line) Nerve Cells Muscle Cells Different culture conditions Different types of differentiated cells

Sources of Embryonic Stem Cells embryos produced through in vitro fertilization they can also come from SCNT cloning Either way, we need embryos in the blastocyst stage. The end result in either case is an embryonic stem cell line. ESCs cannot be collected in vivo!

IVF as a Source of ESCs IVF is the process of fertilization by manually combining an egg and sperm in a laboratory setting IVF procedure generates multiple embryos which are then frozen for storage If these are no longer be needed for fertility purposes they remain frozen or could be destroyed

Somatic Cell Nuclear Transfer

SCNT as a Source for ESCs The cells have the same DNA as the donor (basically we have made an embryonic clone of the person who needs the transplant). These cells can be “customized”; they can be made into any cell/tissue/organ of the body and transplanted (in theory) to the donor without immune rejection. How does this relate to gene therapy?

Concerns About ESCs ESCs from IVF embryos does NOT provide an exact genetic match to a donor. Many of these therapies are still in the infant stages and we don’t know what other challenges will be faced as this technology progresses. How long will a stem cell therapy last? Will these cells “behave” themselves (act at the intended cell type and also not form tumors)? There are some cases of teratoma formation (tumor-like growths) from stem cells.

Adult Stem Cells These cells are derived from various locations in the body (for example, bone marrow, blood, brain) The origin of adult stem cells in some mature tissues is still under investigation These cells are multipotent

Potential Uses of Adult Stem Cells Adult hematopoietic (blood-forming) stem cells from bone marrow have been used in transplants for over 40 years. Scientists have discovered that stem cells exist in the brain and the heart. If the differentiation of can be controlled in the laboratory, these cells could be used in transplantation-based therapies.

Concerns about Adult Stem Cells They are present in only minute quantities and can therefore be difficult to isolate and purify. They may not have the same capacity to multiply as ESCs do. They do not have the development potential of an ESCs. Adult stem cells contain more DNA abnormalities caused by sunlight, toxins, and errors in making more DNA copies during the course of a lifetime.

Umbilical Cord Stem Cells These cells are collected from the umbilical cord of a newborn. These cells are multipotent and have similar uses as adult stem cells The process to collect and store a child’s cord blood is not cheap! The company “Cord Blood Registry”charges an “initial fee” of $2665 and then it is $250 per year for storage

Potential Uses of Umbilical Cord Stem Cells Similar to adult stem cells Why might this blood collection have advantages over bone marrow stem cells?

Amniotic Fluid Stem Cells (AFSC) Stem cells make up about 1% of amniotic fluid These cells, unlike ESCs, do not form tumors. These are a less controversial alternative to ESCs because they are harvested without destroying embryos

Induced Pluripotent Stem Cells (iPSCs) These are “reprogrammed” adult cells so the source could potentially be any somatic cell This is done by the introduction of embryonic genes into the somatic cell This strategy may reprogram available cells into other cell types that have been lost or damaged due to disease. iPSCs could serve as an exact genetic match to patient

Concerns About iPSCs They may not have the same capacity to multiply as other stem cells Unsure about development potential – what if the reprogramming is incomplete? Some of the reprogramming factors are oncogenes

Cloning

Cloning Basics The term clone simply means two things with identical DNA (i.e. identical twins) When we try to clone we need to take the diversity out of reproduction. Instead of using two sources of DNA (the egg and sperm), we use one source of DNA. We have to use an emptied out egg because it contains the molecules necessary for driving early development.

Cloning Procedure Retrieve an egg cell Remove the DNA from the egg cell so that it is “empty” Take a diploid cell from what you want to clone; Add the diploid DNA to the empty egg Let the cell divide into many cells Implant the embryo into the uterus of a surrogate mother to finish development Note: the clone will be genetically identical to the diploid cell that was used in the procedure

How to clone most anything in 5 easy steps! 4 2 3 5 1

Why are scientists interested in cloning animals? To control the selective breeding we are already doing now in dogs “Pharming” Enhance biodiversity by keeping endangered species numbers up Food supply

Reproductive vs. Therapeutic Cloning Now that you know how to clone something, the big difference is whether we are going to pop the embryo into a surrogate mother and let development conclude (this is reproductive cloning) or whether we will harvest the stem cells from the blastocyst and use them (this is therapeutic cloning). Therapeutic cloning involved SCNT.

Regenerative Medicine

What is Regenerative Medicine? Regenerative medicine is a really cool group of technologies used to grow tissues and organs. While some of the technology uses ESCs, there are some other options that dodge the use of ESCs completely

Regenerative Medicine What is the goal of Regenerative Medicine? To create products to improve tissue function To replace diseased or damaged tissue Why Regenerative Medicine? Donor tissues and organs are in short supply Minimize immune system response by using our own cells or novel ways to protect transplanted cells or tissues.

Videos http://www.wakehealth.edu/Research/WFIRM/Our-Story/Our-Story.htm http://www.bloomberg.com/video/70495962-atala-discusses-human-organ-engineering-innovators.html http://www.ted.com/talks/anthony_atala_growing_organs_engineering_tissue.html

Videos: http://www.tengion.com/news/videos.cfm#